Can't find help with email report bugs - anyone with experience willing to help me?

I have been searching online for queries about the reports and can only find a basic how to, no troubleshooting infos. Has no-one had a problem with email reporting? I set up on 10.05 a monthly report and got yesterday the first automatic report spanning back to 2014! When I ask in the system to send me the report now, it is correct, but why did I get one with so much data and why in the middle of the month? I can’t find anywhere troubleshooting with reports. Does anyone have experience and can advise please? I can’t send reports to my customers when the data is not working correctly.